A blood pressure measuring instrument having interest in the present invention is disclosed for example in Japanese Patent Laying-Open No. 4-180728. For example as described in this document a similarity between a cuff pressure waveform and an arterial pressure waveform is utilized and a cuff pressure pulse waveform's areal barycenter position is correlated to a cuff pressure for a maximum amplitude to determine a systolic blood pressure from a diastolic blood pressure.
Mr. Shimazu discloses in an article entitled “Idea to measure diastolic arterial pressure by volume oscillometric method in human fingers,” Medical & Biological Engineering & Computing, Sept. 1986, pp. 549–554 employing volume oscillograph to determine a systolic blood pressure and a mean blood pressure and therefrom determining a diastolic blood pressure.
Furthermore, Japanese Patent Publication No. 5-58335 (Japanese Patent Laying-Open No. 62-292139) discloses utilizing a pressure lower than a systolic blood pressure to obtain a systolic blood pressure by extrapolation.
Japanese Patent Laying-Open No. 4-180728 discloses a method of measurement utilizing a similitude between a cuff pressure pulse wave and an arterial pressure waveform. This method, however, correlates the cuff pressure pulse waveform's areal barycenter position to a cuff pressure exerted when a maximum amplitude appears, and its measurement theory is arguable in validity.
Furthermore, as described in Mr. Shimazu's article, a similitude between a volume pulse waveform and a blood pressure waveform detected via a photoelectric sensor at a finger tip to be measured is utilized to allow a systolic blood pressure to be determined with increased precision, and this requires exerting a cuff pressure to occlude a site to be measured to attain a pressure of no less than a systolic blood pressure.
Japanese Patent Publication No. 5-58335 (Japanese Patent Laying-Open No. 62-292139) discloses exerting a pressure lower than a systolic blood pressure for occlusion to determine a systolic blood pressure. This method, however, calculates the systolic blood pressure by an expression using an experimentally obtained, fixed constant, and thus suffers an error attributed to a variation attributed to a physiological difference between individual subjects.